Relaxation Of Residual Stresses During Cyclic Loading

Author:  Bergstrom, J.
Source:  Proceed.of 4th Conf.of Irish Durab.and Frac.Comm.
Doc ID:  1986038
Year of Publication:  1986
Abstract:  
In annealed, normalized or stress free materials a build-up of residual stress may take place in the surface due to fatigue loading. The residual stress state may however vary during the fatigue process, changing between tensile and compressive values. Shot peened components have mostly fatigue loads above the low-cycle fatigue region, and close to or below the endurance limit. Stress relaxation can occur, and several factors influence its behaviour. It looks as if the direction of the relaxation is determined by mean stress relaxation towards zero, but perhaps to an asymptotic non-zero value. The rate of the relaxation is then given by load amplitudes, stress gradients, environment, history dependant factors, softening/hardening materials parameters and so forth. Variable fatigue loading may result in other rates of relaxation than that expected from constant amplitude loading. An appropriate predictive model has not yet been encountered. Surface and bulk interaction is not discussed in this presentation, although it may be of importance. Descriptors: Steels-- Mechanical properties; Fatigue (materials)-- Stress effects; Residual stress; Stress relaxation; Shot peening